package com.lagou.sqlSession;

import com.lagou.config.BoundSql;
import com.lagou.pojo.Configuration;
import com.lagou.pojo.MapperStatement;
import com.lagou.utils.GenericTokenParser;
import com.lagou.utils.ParameterMapping;
import com.lagou.utils.ParameterMappingTokenHandler;

import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

/**
 * @author ADMIN
 * @date 2021/3/21 19:17
 */
public class SimpleExecutor implements Executor {
    @Override
    public <E> List<E> query(Configuration configuration, MapperStatement mapperStatement, Object... objects) throws Exception {
        //注册驱动获取连接
        Connection connection = configuration.getDataSource().getConnection();
        //获取sql语句
        String sql = mapperStatement.getSql();
        //转换sql语句 转换过程中,还需要对#{}处理 对里面的值进行解析存储
        BoundSql boundSql = getBoundSql(sql);
        //获取预处理对象 preparestatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());
        //设置参数
        //获取到了参数的全路径
        String paramterType = mapperStatement.getParamterType();
        Class<?> aclass = getClassType(paramterType);
        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();
            //反射
            Field declaredField = aclass.getDeclaredField(content);
            //暴力访问
            declaredField.setAccessible(true);
            Object o = declaredField.get(objects[0]);
            preparedStatement.setObject(i + 1, o);

        }
        //执行sql
        ResultSet resultSet = preparedStatement.executeQuery();
        String resultType = mapperStatement.getResultType();
        Class<?> resultTypeClass = getClassType(resultType);

        ArrayList<Object> objectsList = new ArrayList<>();

//        封装返回结果集
        while (resultSet.next()) {
            Object o = resultTypeClass.newInstance();
            //元数据
            ResultSetMetaData metaData = resultSet.getMetaData();
            for (int i = 1; i <= metaData.getColumnCount(); i++) {
                //字段名
                String columnName = metaData.getColumnName(i);
                //字段的值
                Object value = resultSet.getObject(columnName);
                //根据数据库的表和实体的对应关系,完成封装 反射或者内省
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(o, value);
            }
            objectsList.add(o);
        }


        return (List<E>) objectsList;
    }

    private Class<?> getClassType(String paramterType) throws ClassNotFoundException {
        if (paramterType != null) {
            Class<?> aClass = Class.forName(paramterType);
            return aClass;
        }
        return null;
    }

    /**
     * 完成对#{}的解析  1.
     * 1使用?代替  解析出里面的值
     *
     * @param sql
     * @return
     */
    private BoundSql getBoundSql(String sql) {
        //标记处理类: 配置标记解析器来完成对占位符的解析处理工作
        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser = new GenericTokenParser("#{", "}", parameterMappingTokenHandler);
        //解析出来的sql
        String parseSql = genericTokenParser.parse(sql);
        //#{}里面解析出来的参数名称
        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();
        BoundSql boundSql = new BoundSql(parseSql, parameterMappings);

        return boundSql;

    }
}
